The invention relates to an apparatus for the fibre-sorting or selection of a fibre bundle comprising textile fibres, especially for combing. In a known apparatus, fibre sliver is supplied by means of supply device to a fibre-sorting device, especially to a combing device, in which clamping devices are provided, which clamp the fibre bundle at a distance from its free end and a mechanical device is present which generates a combing action from the clamping site to the free end of the fibre sliver in order to loosen and remove non-clamped constituents, such as, for example, short fibres, neps, dust and the like from the free end. For removal of the combed fibre material at least one take-off device is present. The clamping devices each comprise two nipper arms with clamping jaws (upper and lower nipper).
In practice, combing machines are used to free cotton fibres or woollen fibres of natural impurities contained therein and to parallelise the fibres of the fibre bundle. For that purpose, a previously prepared fibre bundle is clamped between the jaws of the nipper arrangement so that a certain sub-length of the fibres, known as the “fibre tuft”, projects at the front of the jaws. By means of the combing segments of the rotating combing roller, which segments are filled with needle clothing or toothed clothing, this fibre tuft is combed and thus cleaned. The take-off device usually consists of two counter-rotating rollers, which grip the combed fibre tuft and carry it onwards.
In order to separate short fibres, neps, dirt and other constituents from a fibre mixture it is known to supply the fibre material in the form of lap rolls to combing machines for mechanical combing-out, the end of the lap web being clamped by a nipper and the end projecting beyond the clamping line, the fibre tuft being mechanically combed-out by means of the comb clothing of a circular comb. The combed-out fibre bundle is then transferred to a detaching roller pair where it is in turn formed into a coherent web, or “pieced”. When the fibre bundle is removed from the nipper by the detaching rollers, the end severed from the lap is likewise pulled through a mechanical top comb, so that as far as possible no short fibres, neps, dirt and other undesirable constituents remain in the combed web. A disadvantage of that known combing method is, in particular, the discontinuous mode of operation, in which large masses have to be accelerated and decelerated during the operating cycle.
The back and forth swinging movement of the nipper assembly gives rise to very substantial vibration, especially in the case of high nip rates, which on the one hand requires the drive elements and bearing elements to be of suitably stable construction and on the other hand places high demands on the framework of the machine as well as on the base on which the machine is mounted.
In order to be able to remove the partially cleaned fibres from the jaws of the nipper unit using the rollers of the take-off device, either the relatively heavy take-off device needs to move linearly or over part of an arc of a circle to the fibre bundle held between the jaws of the nipper arrangement or, the other way round, the nipper arrangement has to be moved towards the stationary take-off rollers. In the case of the 450 nips per minute usually required, the large masses being moved result in a high level of dynamic agitation of the entire combing machine which limits its operating speed and productivity.
Furthermore, a problem of conventional combing machines is that when the combed fibres are removed by the counter-rotating take-off rollers, up to 50% of the fibre length has not been cleaned by the circular comb, because during the combing process, that is to say when the combing segment passes, the fibres were clamped between the jaws of the nipper arrangement or were located behind the jaws, seen in the transport direction. In order also to clean that portion of the fibres as well as possible, those fibres are conventionally pulled through a top comb arranged in front of the take-off rollers. The top comb is an additional structural element for every combing head.
The detaching roller pair, consisting of a lower detaching roller and an upper detaching roller, is directly adjacent to the nipper apparatus and the circular comb. The lower detaching roller is located between the path of movement of the comb tips of the circular comb and the upper detaching roller and, together with the upper detaching roller, forms the clamping nip for the combed bundles. The nipper arrangement is mounted so as to swing in two directions. Firstly, it is moved, at a distance from the detaching roller pair, towards the path of movement of the comb tips of the circular comb. In that position, the combing of the fibre bundle is carried out by the circular comb. When that operation is complete, the nipper apparatus is raised as a unit so that the fibre bundle that has just been combed arrives in front of the clamping nip of the detaching roller pair. During that movement, the nipper apparatus also approaches the detaching roller nip horizontally. The portion of combed sliver conveyed back at that time point is overlapped with the tips of the new, combed fibre bundle, compressed in the clamping nip of the detaching rollers and drawn in the take-off direction by the detaching rollers, the top comb being inserted into the end of the fibre bundle that has just been combed and combing out that free piece of fibre. As a result of the receding movement of the nipper apparatus and the take-off movement of the detaching roller pair, the combed fibre bundle is detached and a fresh fibre bundle is supplied to the nipper apparatus by the feed roller, clamped and brought into the combing position relative to the circular comb. Such an arrangement is disadvantageous because, in particular, the nipper apparatus has to perform a variety of very large movements with greater or lesser degrees of acceleration. The operating speed is thus considerably limited, a large amount of noise is generated and the inertial forces that arise result in above-average wear. Adjustment of the detaching distance and the feed quantity can be effected only while the machine is stationary. A further crucial disadvantage is that the free end of the fibre bundle that has just been combed also has to be moved at relatively high speed, with its free fibre tips to the front, over large distances and placed in an exactly defined position onto the returned end of the combed sliver. In dependence upon the air vortices that occur and the respective air resistance, the fibre bundle is frequently incorrectly positioned on the returned combed sliver so that it is necessary to operate at relatively low speeds. In any case, however, losses of quality are observed in the combed sliver. A further disadvantage of the known apparatus is that uncontrolled fold-formation occurs between the detaching roller pair and the take-off rollers as a result of the pilgrim-step motion of the detaching rollers, which additionally results in disruption of the combing process.
When the nipper is located in its forward position, it is opened and transfers the combed-out fibre bundle to the detaching roller pair that bundle being pieced with the previously detached fibre bundle.
The known cotton-combing process is a discontinuous process. During a nipping operation, all assemblies and their drive means and gears are accelerated, decelerated and in some cases reversed again. High nip rates result in high acceleration. Particularly as a result of the kinematics of the nippers, the gear for the nipper movement and the gear for the pilgrim-step movement of the detaching rollers, high acceleration forces come into effect. The forces and stresses that arise increase as the nip rates increase. The known flat combing machine has reached a performance limit with its nip rates, which prevents productivity from being increased. Furthermore, the discontinuous mode of operation causes vibration in the entire machine which generates dynamic alternating stresses.
EP 1 586 682 A discloses a combing machine in which, for example, eight combing heads operate simultaneously one next to the other. The drive of those combing heads is effected by means of a lateral drive means arranged next to the combing heads having a gear unit which is in driving connection by way of longitudinal shafts with the individual elements of the combing heads. The fibre slivers formed at the individual combing heads are transferred, one next to the other on a conveyor table, to a subsequent drafting system in which they are drafted and then combined to form a common combing machine sliver. The fibre sliver produced in the drafting system is then deposited in a can by means of a funnel wheel (coiler plate). The plurality of combing heads of the combing machine each have a feed device, a pivotally mounted, fixed-position nipper assembly, a rotatably mounted circular comb having a comb segment for combing out the fibre tuft supplied by the nipper assembly, a top comb and a fixed-position detaching device for detaching the combed-out fibre tuft from the nipper assembly. The nipper assembly comprises a lower nipper, which co-operates with an upper nipper plate. The upper nipper plate is here pivotally mounted on the lower nipper by way of a pivot axis. The lower nipper and the upper nipper are formed with complementary profiles at their front end region, via which, when the nipper assembly is closed, they clamp the lap supplied via a feed cylinder. The fibre tuft protruding in this clamped position from the nipper assembly is combed by a comb segment of a circular comb. The circular comb arranged beneath the nipper assembly is secured, without relative rotation, on a circular comb shaft, which is connected via the drive connection to a gear mechanism. The drive of the gear mechanism is effected by a main motor. The nipper assembly is pivotally mounted on the axis of the circular comb shaft via one (or two) pivot arm(s). The free end of the pivot arm is fixedly secured to the frame of the lower nipper. In its rear region, the lower nipper has a pivot axis, on which a lever is rotatably mounted. This lever is rotatably secured via an axle to a crank disc. The axle of the crank disc is in connection via a drive connection with a drive motor. The nipper parts are steel plates with a contour worked therein for clamping the fibre lap. The nipper parts are secured to the nipper assembly oscillating back and forth. The clamping force of about 300N is generated by an eccentric shaft with compression spring. Its function is to clamp the lap during combing, and to align it in a downward direction towards the circular comb roller. During the detaching operation, the nipper is open. Disadvantages of that combing machine are especially the large amount of equipment required and the low hourly production rate. There are eight individual combing heads which have in total eight feed devices, eight fixed-position nipper assemblies, eight circular combs with comb segments, eight top combs and eight detaching devices. A particular problem is the discontinuous mode of operation of the combing heads. Additional disadvantages result from large mass accelerations and reversing movements, with the result that high operating speeds are not possible. Finally, the considerable amount of machine vibration results in irregularities in the deposition of the combed sliver. Moreover, the ecartement, that is to say the distance between the nipper lip of the lower nipper plate and the clamping point of the detaching cylinder, is structurally and spatially limited.